Determining JavaScript cookie support in client's
browser

If your script relies on JavaScript cookies to persist and store
information for retrieval later, it's good practice to always make sure
that the user's browser supports cookies first. This includes whether the
browser has cookies enabled (an option in most browsers). Depending on
your situation you can then either remind the user to enable cookies, or
create code to handle these cases silently.

So, to answer this common question, use the following technique to
detect whether the client's browser has cookies enabled:

Firstly, we use the official property for the task, navigator.cookieEnabled, to help determine whether the browser
has cookies enabled. However, we immediately run into a limitation- this
property is supported only in IE4+ and NS6+. So, in both cases where the
property returns false or does not exist (in other browsers), we set the
variable cookieEnabled
to false instead for continued investigation.

Moving on, it's now time to probe all other browsers for cookie
availability. The age-old "give it a try" technique works nicely. By
setting a dummy value to document.cookie
and immediately probing it to see if the value is retained, we can
tell if cookies is enabled on the client's end.

The variable cookieEnabled now
contains a Boolean value indicating the client's cookie support. Nice and
crunchy!